We find that the current increases with input power for all antennas under the same phase, consistent with Fig. REF . The ratios between them are independent of input power and they are \(I_{A_1}/I_{A_0}\approx 0.150\) , \(I_{A_2}/I_{A_0}\approx 0.146\)  and \(I_{A_2}/I_{A_1}\approx 0.973\) , respectively. Compared with Fig. REF , one can see that the ratios are much higher, indicating better coupling between antennas with the existence of plasma. Since the induced power origins from \(A_0\)  and the distance between \(A_1\)  and \(A_0\)  is shorter than that between \(A_2\)  and \(A_0\) , it is reasonable to have \(I_{A_2}/I_{A_1}<1\) . Again, we draw the magnetic flux surrounding these antennas (Fig. REF ), and analyse these ratios referring to transformer but with the inclusion of plasma. As pointed in early references[1]}, [2]}, a stabilised plasma can be paramagnetic, and could increase the magnetic permeability and confine the magnetic flux, behaving similarly to the magnetic core for a transformer. This surely enhances the coupling effect among antennas and thereby the ratios of induced current. Please note that although plasma cannot be treated as normal magnetic material[3]}, the gyrating motions of charged particles do provide additional magnetic moment, in form of \(\mu _m=m v_\perp ^2/2B\) , which leads to the increased effective magnetic permeability (\(\mu _{e}=\mu _0+\mu _m\) ).
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